This invention relates generally to photovoltaic generating structures. More specifically, the invention relates to roof-mounted photovoltaic generating structures and methods for mounting flexible, photovoltaic roofing material onto a roof or deck structure.
Photovoltaic devices provide silent, nonpolluting, reliable sources of electrical energy. Rooftops and other portions of building structures provide ideal support surfaces for photovoltaic devices, and a large body of art has been developed relating to methods and apparatus for mounting photovoltaic structures onto buildings.
Thin film photovoltaic devices are particularly advantageous since they are relatively low in cost, flexible, and capable of being manufactured in relatively large areas, by continuous deposition processes. Such thin film devices can be encapsulated in transparent, durable, flexible polymeric bodies, and are ideally suited for building-mounted installations. In some instances, roofing materials can actually be fabricated from webs of photovoltaic material. Such configurations can function as a roofing material and can also provide large amounts of electrical power.
A first example of a photovoltaic array module incorporating a plurality of photovoltaic cell strips is set forth in U.S. Pat. No. 4,574,160, issued to Cull et al. Each cell strip incorporates an electrically conductive substrate layer, a semiconductor body deposited on the substrate layer, and a transparent electrically conductive layer deposited on the semiconductor body. Electrically conductive filaments are alternately connected to contact points on the substrate layer of one cell strip and to contact points on the transparent electrically conductive layer of another cell strip. First and second bus bars are connected to the end of the cell strips of the array to collect the electrical energy created thereby.
A further example of the prior art is set forth in U.S. Pat. No. 4,860,509, issued to Laaly et al., and which teaches a combination form of flexible roofing material including a reinforced single-ply membrane base for adhering to a roof substrate. Laminated upon the base is a structurally flexible layer of solar cells encapsulated and sealed in a flexible intermediate layer of solar radiation transparent plastic protected by a cover layer of weatherproof solar transparent plastic. The roofing is further manufactured as elongated sheets which are rolled up for transport to the site and installed by such as sealing to adjacent sheets of similar single-ply membrane material which may or may not incorporate solar cells.
The present invention, as will be described in greater detail hereinbelow, is directed to an apparatus and method for mounting relatively large area webs of photovoltaic roofing material onto building structures and, in particular, to a peaked roof of such a structure. As known in the pertinent art, such photovoltaic roofing materials are capable of absorbing solar ambient light for conversion into a suitable electrical output.
A plurality of individual and, preferably elongated, webs of photovoltaic material are provided. Each of the webs is preferably of flexible thin film and with a typically centralized and photovoltaically active area. The webs of photovoltaic material typically vary in either or both length and width and may exhibit differing voltage ratings, such as 6, 12, 18, 24 volts.
The photovoltaic material is encapsulated within a polymeric material, projecting beyond both the extending sides and end of the photovoltaically active area, and resistant to ambient conditions. A top surface of the polymeric material is also transparent to photovoltaically active wavelengths. Contact terminals are located in extending fashion from a selected end of each elongated web of photovoltaic material and, as will be further described, function to electrically interconnect the associated web to either additional extending webs or to an electrical junction box or other suitable connector device.
Each succeeding web of material is disposed in a longitudinally extending and partially overlapping relationship upon the exterior surface of the roof structure and so that a first extending edge of a first web is arranged proximate a second extending edge of a further associated web. Additional components such as clamping strips are provided and are configured to engage the first and second webs along their proximate extending edges. Batten caps are affixed to the clamping strips and further function to retain the photovoltaic roofing material on the roof as well as to provide a moisture resistant seal and decorative cover to the clamping strips.
In preferred installation applications, the elongated webs of photovoltaic material extend in a general direction from a lower eave edge of the roof to either an intermediate step and/or from the step to an uppermost ridge, these forming a conventionally known gable end roof. A further hip roof application contemplates the webs of photovoltaic material extending between a valley and ridge of the hip roof, as well as along an extending eave soffit.
Additional installations permit opposing ends of elongated photovoltaic webs to be electrically connected, given structural variations or offsets in pitch which are inherent in eave or ridge cap locations of such roofing structures. The eave and ridge cap applications further permit the installation of such as junction boxes and/or other electrical components.
Yet additional applications of the present invention include the provision of a transport and storage spool and upon which may be wound an overall length of the photovoltaic material. A removable cover of the spool reveals an interior storage compartment suitable for holding such as assembly tools and other devices or implements necessary for installing the photovoltaic material.
A reel stand is provided for dispensing the photovoltaic material from the transport and storage spool. In a further application, the reel stand may be configured to be mounted in a horizontally traversable and underside eave location of the roofing structure and to facilitate drawing, sectioning and affixing lengths of photovoltaic material from the spool and along the roof.
The mounting system of the present invention is readily adaptable to conventional building practices and enables the quick and accurate installation of photovoltaic roofing systems without the need for special training of workers or extensive modifications to conventional building design. These and other advantages will be apparent from the succeeding description of the Figure illustrations and detailed description, which follow.